Recently, a diagnosis based on an image is widely implemented. For instance, an intended diagnosis of a subject body is implemented on the basis of three-dimensional image data which is obtained by an X-ray CT (computed tomography) device or the like and which represents an appearance of a portion within the subject body.
The CT device is configured to move the subject body in a direction of its axis while continuously turning an X-ray irradiator or detector, for performing continuous helical scanning of a three-dimensional region of the subject body, to generate a three-dimensional tomographic image by superimposing continuous slices of the three-dimensional region on each other.
An example of such a three-dimensional image is a three-dimensional image of a truncus vascular region or a bronchial region of a lung. The three-dimensional image of the vascular region is obtained for accurate detection of a three-dimensional structure prior to a colonic cancer operation, for example, to determine a colonic part to be excised, and the vascular parts to be ligated (by a ligature). For diagnosing the lung cancer to determine a bronchus around which the lung cancer exists, it is necessary to clearly display a tree structure of the bronchus at the position of the lung cancer.
Patent Document 1 (JP-2000-135215 A) discloses an example of a known method of displaying an image of a luminal organ, which method uses a device for navigation of a bronchial endoscope to a target region of a bronchus of the subject body, by generating a three-dimensional image of a duct or tube within the subject body on the basis of image data of a three-dimensional region of the bronchus, obtaining a path to a target point along the duct within the generated three-dimensional image, generating a virtual endoscopic image of the duct along the path, on the basis of the image data, and displaying the generated virtual endoscopic image.
However, the above-described prior art method for internal observation of the subject body suffers from extreme difficulty in detecting a positional relationship with the adjacent or neighboring other organs. Accurate detection of the luminal structure together with the positional relationship with the other organs is essential and important irrespective of imaging diagnosis, endoscopic inspection or operation, and laparotomy (abdominal incision). In this respect, there has been a need of an assisting system to facilitate such diagnosis, inspection, operation and laparotomy.
On the other hand, it is necessary to extract suitable information of a desired organ, for example, luminal information of the bronchus, from the image data of the three-dimensional region, for generating the three-dimensional image of the duct within the subject body, on the basis of the three-dimensional data of the subject body. In this respect, non-Patent Document 1 (T. Kitasaka, K. Mori, J. Hasegawa and J. Toriwaki: “A Method for Extraction of Bronchus Regions from 3D Chest X-ray CT image by Analyzing Structural Features of the Bronchus”, Forma 17. pp. 321-338 (2002)), for example, proposes a so-called “segmentation processing”, which comprises setting a VOI (volume of interest) of a predetermined size consisting of predetermined voxels of the three-dimensional region of the subject body, and extracting suitable information of a desired organ, for example, luminal region information of the bronchus, from the image data of the three-dimensional image data within the VOI, while segmenting the VOI in the direction of the axis of the subject body    Patent Document: JP-2000-135215 A    Non-Patent Document 1:    T. Kitasaka, K. Mori, J. Hasegawa and J. Toriwaki: “A Method for Extraction of Bronchus Regions from 3D Chest X-ray CT image by Analyzing Structural Features of the Bronchus”, Forma 17. pp. 321-338 (2002)    Patent Document 2: JP-2004-180940 A    Patent Document 3: WO 2004/010857 A1    Patent Document 4: JP-2006-68351 A    Patent Document 5: JP-2004-230086 A    Patent Document 6: JP-2000-163555 A    Patent Document 7: JP-2003-265408 A